Engine starter gearing



y 1952 D. MILLER 2,595,802

ENGINE STARTER GEARING Filed Sept. 29, 1950 2 SHEETSSHEET l as 68 .31 35 38 j as 1719 2733 29 56 34 a 1 VE WITNESS: 600 a Z' Z- ATTOBNE Y y 1952 D. L. MILLER 2,595,802

ENGINE STARTER GEARING Filed Sept. 29, 1950 2 SHEETSSHEET 2 as as 171.9 2? 365554 .36

IN V EN TOR.

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ORNE Y Patented May 6, 1952 ENGINE STARTER GEARIN G Donald L. Miller, Horseheads. N. Y., assignor to Bendix Aviation Corporatiom'Elmira' Heights, N. Y., a corporation of Delaware Application September 29, 1950,Seria-l No. 187,586

8 Claims.

'1 The present invention relates to engine'starter gearing, and more particularly to an automatically-engaging drive which is arranged to main-' tain its engagement with the engine until the engine is reliably self-operative.

It is an object of the present invention to provide a novel engine starter drive of the above type includingan overrunning connection between the starting motor and engine, and means for holding the gearing in mesh until the engine has overrun the starting motor for a predetermined number of revolutions.

It is another object to provide such a device in which the overrunning connection also provides a coupling'which slips when subjected to a predeterminedoverload.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly broken away and in section of a preferred embodiment of the invention showing the parts in idle position.

Fig. 2 is a similar View showing the parts in cranking position.

Fig. 3 is a similar view showing the parts in position assumed after the engine starts and overruns the drive; and

Fig. 4 is a section taken substantially on the line 4--4 of'Fig. 3. I

In Fig. 1 of the drawing there is illustrated a power shaft I on which a screw shaft 2 i rigidly mounted by any'suitable means such as the keys 3 and set screw 4. A control nut 5 is threaded on the screw shaft and confined thereon by a stop nut -6 which is rigidly anchored onthe end of the screw shaft. Movement of the control nut 5 away from the stop nut 6 is limited by a back stop 1 anchored to the screw shaft by the set screw 4.

A pinion 8 is slidably journalled on the power shaft l for movement into and out of mesh with a gear 9 of the engine to be started. Means for actuating the pinion from the control nut 5 is provided comprising a barrel member H splined as indicated at 12 on the extended hub I3 of pinion 8, being retained thereon by a lock ring 14, the pinion 8 being normally held in extended relation by a mesh-enforcing spring l5 located between the end of the barrel and a shoulder 16 on the pinion.

A driving clutch member I! is splined as indicated at I8 on the control nut 5 and is pressed against a lock ring l9 on the control nut by a heavy compression spring here shown in the form of a pair of spring washers 2| which are retained by a lock ring 22. Driving clutch member IT has a loose bearing fit in the barrel H and is retained therein by a lock ring 23. Driving clutch member I! is provided with projections or teeth 24 adapted to cooperate with corresponding teeth 25 of a driven clutch member 26 which is splined as shown at 21 within the barrel I l. A light compression spring 28 is located between the driven clutch member 23' and the stop nut 6, which spring normally maintains the driven clutch member in engagement with the driving clutch member I1, and also serves to assist in retaining the drive in idle position.

Means are provided for holding the pinion 8 in mesh with the engine gear 9' after the engine starts so as to maintain such engagement until the engine is reliably self-operated. As here shown, this means comprises a rod 29 slidably journalled in the stop nut 6 and provided with an inclined thread 3| intermediate its length. At one end, the rod 29 has a swivel connection with the control nut 5 by means of a thrust ring 32 seated in the control nut and engaging in a groove 33' formed in the rod. The groove 33 is considerably wider than the thrust ring 32 so as to provide for longitudinal lost motion in the swivel connection. A latch member 34 is slidably mounted in a radial opening 35 in the stop nut 5, and is pressed against the rod 29 by means of a spring ring 36 so as to engage the thread 3| of the rod when the parts are in driving position as illustrated in Fig. 2, thereby preventing demeshing movement of the control nut.

Means are provided for rotating the rod 29 so as to cause it to thread itself by the latch 34 when the barrel ll overruns the screw shaft 2. For this purpose a toothed wheel 31 is fixedly mounted on the end of the rod 29 and an actuating member 38 (Fig. 4) provided with one or more corresponding teeth is rigidly mounted in the interior of the barrel II in position to engage and rotate the toothed gear 31 in the direction to cause it to move to the left in Fig. 1 past the latch member 34. The latch 34 and the threads 3| on the rod 29 are of saw tooth form in section; so that the rod can ratchet past the latch in the meshing direction, but the rod is required to thread itself past the latch in the demeshing operation.

In operation, starting with the parts in the positionsillustrated in Fig. 1, rotation of the power shaft I in the direction of the'ar'row a causes the control nut 5 to threaditself along the screw shaft 2 until its longi tiidinal movement is arrested by the stop nut 6 as shown in Fig. 2, at which time the pinion 8 is fully meshed with the engine gear 9. At this time the driven clutch member 26 is also brought into engagement with the stop nut 6, this movement being permitted by the ratcheting of the rod 29 past the latch 34. Cranking torque is thereafter transmitted from the screw shaft 2, control nut 5, and driving clutch member H to the driven clutch member 26, barrel II, and pinion 8 to rotate the engine gear 9. If the initial torque exceeds a predetermined maximum, the teeth 24, 25 of the clutch members I1, 26 may slip over each other, correspondingly compressing the heavy spring 2|, so that peak loads may thus be slipped off. During the normal cranking operation the spring 2! will be partially compressed as shown in Fig. 2, but not sufficiently to allow slippage of the clutch members to take place.

When the engine fires, the acceleration of the pinion 8, and barrel ll causes the driven clutch member 26 to rotate faster than driving clutch member II. The driving clutch member therefore returns to its normal position on the control nut against the lock ring I9, after which the control nut is caused to move backward slightly on the shaft 2, thus permitting the driven clutch member 26 to overrun the driving clutch member I1. This initial backward movement of the control nut is permitted by the lost motion in the swivel connection 32, 33 with the threaded rod 29. This allows the driven clutch member 26 and barrel I l to overrun the control nut and screw shaft, whereupon the toothed member 38 engages and rotates the wheel 31 thereby causing the rod 29 to thread itself past the latch 34 as shown in Fig. 3 of the drawing.

In case of a false start, as soon as the engine gear 9 slows down below the speed of the power shaft, pinion 8 is again moved into full mesh with the engine gear 9 and cranking is resumed. When the engine becomes reliably self operative, the overrunning of the barrel l I rotates the threaded rod 29 so that after a predetermined number of revolutions the drive is released from engagement and returned to idle position by the overrunning action of the control nut 5 on the screw shaft 2 assisted by the spring 28 which thereafter maintains the parts in idle position.

Although but one form of the invention has been shown and described in detail, it will be understood that various changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an engine starter drive a power shaft, a pinion slidably journalled thereon for longitudinal movement into and out of mesh with a gear of the engine to be started, a hollow screw shaft fixed on the power shaft, a control nut threaded on the screw shaft, means for actuating the pinion from the control nut including a driving clutch member splined on the control nut, a barrel member non-'rotatably connected to the pinion, a driven clutch member non-rotatably mounted in the barrel, a stop for the driven clutch member and the control nut, defining the operative position of the control nut and pinion, and a yielding abutment for the driving clutch member on the control nut.

2. An engine starter drive as set forth in claim 1 including further spring means normally holding the clutch members in engagement but permitting the driven clutch member to overrun the driving clutch member when the engine starts.

3. An engine starter drive as set forth in claim 2 including further means for restricting longitudinal movement of the control nut away from the engine gear so as to hold the pinion in mesh with the engine gear until it has overrun the control nut a predetermined number of revolutions.

4. An engine starter drive as set forth in claim 2 including further a threaded rod slidably journalled in said stop, having a swivelled connection with the control nut, a latch in the stop engaging the threads of the rod, and means for rotating the rod when the barrel overruns the control nut.

5. In an engine starter drive a power shaft, a screw shaft fixed thereto, a pinion slidably journalled on the power shaft, a control nut threaded on the screw shaft, means including a barrel member connecting the control nut and pinion, a stop nut on the screw shaft limiting the travel of the control nut, a threaded rod slidably journalled in the stop nut and having a swivel connection with the control nut, a latch in the stop nut engaging the threads of said rod, and means in the barrel for rotating the rod when the barrel rotates with respect to the stop nut.

6. An engine starter drive as set forth in claim 5 in which the connection between the control nut and pinion also includes a pair of clutch members, light spring means normally holding the clutch members in engagement but permitting the driven clutch member to overrun the driving clutch member, and torque-responsive means for subjecting the clutch members to a predetermined maximum pressure for the transmission of cranking torque therethrough.

7. In an engine starter drive a power shaft, a hollow screw shaft fixed thereon, a control nut threaded on the screw shaft, a stop nut fixed on the screw shaft forming an abutment for the con trol nut; a pinion slidably journalled on the power shaft for movement into and out of mesh with a gear of the engine to be started, means for actuating the pinion from the control nut including a barrel non-rotatably connected to the pinion with freedom for limited relative longitudinal movement, a driving clutch member splined on the control nut and rotatable within the barrel, a driven clutch member splined in the barrel, a light compression spring in the barrel between the driven clutch members and the stop nut on the screw shaft, and a heavy compression spring on the control nut resisting movement of the driving clutch member away from the driven clutch member.

8. An engine starter drive as set forth in claim '7 including further a threaded rod slidably journalled in the stop nut and having a swivel connection with the control nut at one end, a latch in the stop nut engaging the threads of the rod when the parts are in cranking position; a toothed wheel on the other end of the rod, and actuating means in the barrel engageable with said wheel to rotate the wheel and rod when the pinion and barrel overrun the screw shaft.

DONALD L. MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,163,841 Kearney June 27, 1939 2,546,948 Miller Mar. 27, 1951 

